This invention relates to an accelerator pedal for an electronic throttle actuation system. More specifically, the invention relates to an improvement in creating hysteresis that acts on the pedal shaft so that the "feel" of pedal operation simulates that which exists in a pedal that is coupled to the throttle strictly by mechanical coupling systems.
In an electronic throttle actuation system for an automotive internal combustion engine, the position of the throttle blade is controlled by an actuator which receives an electrical signal from an electronic control unit. The electronic control unit in turn receives an input signal from a pedal assembly located in the occupant compartment of the vehicle and the system functions to cause the throttle blade to be under the control of the pedal assembly The pedal assembly comprises a transducer that provides to the electronic control unit a signal representative of the desired degree of throttle actuation. The assembly also comprises a return spring mechanism that urges the pedal to a position corresponding to the throttle blade being in a nearly closed, or idle, position. Depressing the pedal from this idle position rotates the pedal shaft against the spring, and in turn the electronic control unit supplies an appropriate signal to the actuator causing the throttle blade to be positioned to the extent commanded by the amount of depression of the pedal. In order for the pedal assembly to simulate the "feel" of throttle actuation systems that are strictly mechanical in nature, it is necessary for the pedal assembly that is used in the electronic throttle control system to comprise a friction means that imparts hysteresis, or dampening, to the pedal shaft. It is this feature that is the subject of the above-referenced patent application.
The present invention relates to improvements in a pedal assembly for an electronic throttle control system that are directed to the means for imparting hysteresis to the pedal shaft. In a first embodiment of the present invention, a disk is affixed to the pedal shaft and a pair of friction pads are disposed on opposite sides of the disk. The friction pads are urged resiliently against the opposite sides of the disk by means of a spring metal clip that contains the friction pads. In a second embodiment of the present invention, the friction elements are a pair of friction rings that are affixed to opposite faces of the disk. A pair of metal rings on opposite sides of the disk are resiliently urged against the friction rings. In both embodiments of the invention, rotation of the pedal shaft causes a frictional effect to be generated in resistance to the rotational motion of the pedal shaft. The "feel" of the pedal assembly is thereby caused to simulate the feel that is encountered in throttle actuation systems that utilize strictly mechanical coupling means between the pedal and the throttle blade.
The foregoing features, advantages and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.